1. Field of the Invention
The present invention relates generally to diamond enhanced carbide inserts that can be used for performing mechanical actions, such as drilling through rock or other hard materials, that require high wear and impact resistance. More specifically, the present invention relates to diamond enhanced carbide inserts that have improved interface strength and also improved residual stress distribution.
2. Description of Related Art
Polycrystalline diamond compacts, buttons, cutters, inserts, and cutting tools (hereinafter referred to as "inserts") are widely used in bits such as those for oil field drilling and mining operations as well as in the cutting tool industry. A typical insert is composed of an abrasion resistant material embedded into or covering a substrate.
While many inserts are made from carbide only, diamond enhanced inserts are manufactured by bonding a layer or other concentrated mass of polycrystalline diamond onto or into a sintered carbide substrate by the application of high pressure and temperature in a manner well known to those skilled in the art. One such method involves sintering the polycrystalline material directly to a cemented carbide substrate by means of high pressure and high temperature. This method of forming inserts is in wide use in the diamond enhanced carbide insert industry. During this process, cobalt, nickel, iron or similar metals are used to act as a sintering aid for the diamond. Such metal may be premixed with the diamond, or swept from the substrate into the diamond, forming a matrix which bonds the diamond and carbide together at the interface and facilitates the formation of solid polycrystalline diamond.
When in operation, an insert is subject to enormous stress. Such stress is a cause of crack initiation and subsequent failure. Delamination, exfoliation and fracture are typical failure types. A variety of loading conditions may be experienced by inserts due to variation in application and geologic formation. The mechanics which dictate insert failure are further complicated by complex residual stresses which result in inserts due to the mismatch of thermal expansion coefficient and elastic modulus of dissimilar materials during processing. Failure mechanisms are therefore varied and failure criteria are not well established. Because of this limited understanding, one would expect that a diversity of attempts to make impact and wear resistant inserts have been undertaken. The works listed below are related to previous contributions to the engineering of inserts and some of their relevant components.
U.S. Pat. No. 2,264,440 describes a diamond abrasive drill bit for drilling holes for blasting or grouting where no core is required.
U.S. Pat. No. 3,745,623 describes diamond tools and superpressure processes for the preparation thereof, the diamond content being supported on and being directly bonded to an extremely stiff substrate, often made of sintered carbide.
U.S. Pat. No. 3,767,371 discloses abrasive bodies that comprise combinations of cubic boron nitride crystals and sintered carbide.
U.S. Pat. No. 3,841,852 describes abraders, abrasive particles and methods for producing same, where the preferred primary abrasive is a diamond.
U.S. Pat. No. 3,871,840 reveals how abrasive particles are improved in function by encapsulating them with a metallic envelope.
U.S. Pat. No. 3,913,280 describes a polycrystalline diamond composite and a method for forming diamond to diamond bonds between adjacent diamond particles.
U.S. Pat. No. 4,156,329 describes a method for fabricating a drill bit comprised of a plurality of composite compact cutters.
U.S. Pat. No. 4,268,276 describes a compact for cutting, drilling, wire drawing and shaping tools, consisting essentially of a porous mass of self-bonded, boron-doped diamond particles and catalyst-solvent material.
U.S. Pat. No. 4,311,490 discloses an improved process for preparing a composite compact wherein a mass of abrasive crystals, a mass of metal carbide, and a bonding medium are subjected to a high-temperature/high pressure process for providing a composite compact. The resulting composite compact is also disclosed therein.
U.S. Pat. No. Re. 32,036 discloses a drill bit for connection on a drill string, the drill bit having a hollow tubular body with an end cutting face and an exterior peripheral stabilizer surface with cylindrical sintered carbide inserts positioned therein.
U.S. Pat. No. 4,592,433 discloses a cutting blank that comprises a substrate formed of a hard material and including a cutting surface with a plurality of shallow grooves that contain strips of a diamond substance.
U.S. Pat. No. 4,604,106 reveals a composite polycrystalline diamond compact comprising at least one layer of diamond crystals and precemented carbide pieces which have been pressed under sufficient heat and pressure to create composite polycrystalline material wherein polycrystalline diamond and the precemented carbide pieces are interspersed in one another.
U.S. Pat. No. 4,605,343 discloses a sintered polycrystalline diamond compact having an integral metallic heat sink bonded to and covering at least he outer diamond surface.
U.S. Pat. No. 4,629,373 discloses a polycrystalline diamond body with a plurality of faces having enhanced surface irregularities over at least a portion of at least one of the faces, the polycrystalline diamond body with the enhanced surface irregularities being attached to other materials such as metal.
U.S. Pat. No. 4,694,918 describes an insert that has a tungsten carbide body and at least two layers at the protruding drilling portion of the insert. The outermost layer contains polycrystalline diamond and the remaining layers adjacent to the polycrystalline diamond layer are transition layers containing a composite of diamond crystals and precemented tungsten carbide, the composite having a higher diamond crystal content adjacent the polycrystalline diamond layer and a higher precemented tungsten carbide content adjacent the tungsten carbide layer.
U.S. Pat. No. 4,764,434 reveals a polycrystalline diamond tool comprising a diamond layer bonded to a support body having a complex, non-planar geometry by means of a thin and continuous layer of a refractory material applied by a coating technique, such as PVD or CVD.
U.S. Pat. No. 4,811,801 describes an insert that includes a polycrystalline diamond surface on an insert body having a head portion made from a material with elasticity and thermal expansion properties advantageously tailored for use in rock bits, as well as rock bits made with such inserts.
U.S. Pat. No. 4,913,247 describes a drill bit having a body member with cutter blades having a generally parabolic bottom profile.
U.S. Pat. No. 5,016,718 reveals a polycrystalline diamond cutting element whose mechanical strength is improved due to the fact that the edge of the element is rounded with a small visible radius.
U.S. Pat. No. 5,120,327 describes a composite for cutting in subterranean formations, comprising a cemented carbide substrate and a diamond layer adhered to the surface of the substrate.
U.S. Pat. No. 5,135,061 describes a preform cutting element for rotary drill bit for use in drilling or coring holes in substrate formations which includes a cutting table of superhard material such as polycrystalline diamond.
U.S. Pat. No. 5,154,245 relates to a rock bit insert of cemented carbide for percussive or rotary crushing rock drilling. The button is provided with one or more bodies of polycrystalline diamond in the surface produced at high pressure and high temperature in the diamond stable area. Each diamond body is completely surrounded by cemented carbide except the top surface.
U.S. Pat. No. 5,158,148 describes cemented tungsten carbide rock bit inserts having diamond particles dispersed therein for enhanced hardness and wear resistance.
U.S. Pat. No. 5,217,081 relates to a rock bit insert of cemented carbide provided with one or more bodies or layers of diamond and/or cubic boron nitride produced at high pressure and high temperature in the diamond or cubic boron nitride stable area. The body of cemented carbide has a multi-structure containing eta-phase surrounded by a surface zone of cemented carbide free of eta-phase and having a low content of cobalt in the surface and a higher content of cobalt next to the eta-phase zone.
U.S. Pat. No. 5,248,006 describes a cutting structure having diamond filled compacts for use in an earth boring bit of the type having one or more rotable cones secured to bearing shafts.
U.S. Pat. No. 5,264,283 relates to buttons, inserts and bodies that comprise cemented carbide provided with bodies and/or layers of CVD- or PVD-fabricated diamond and then high pressure/high temperature treated in the diamond stable area.
U.S. Pat. No. 5,279,375 describes a multidirectional drill bit cutter comprising a cylindrical stud having a layer of polycrystalline diamond formed thereabout.
U.S. Pat. No. 5,335,738 relates to a button of cemented carbide. The button is provided with a layer of diamond produced at high pressure and high temperature in the diamond stable area. The cemented carbide has a multi-phase structure having a core that contains eta-phase surrounded by a surface zone of cemented carbide free of eta-phase.
U.S. Pat. No. 5,351,772 discloses a substantially polycrystalline diamond compact element for drilling subterranean formations. The cutting element includes a cemented carbide substrate having radially extending raised lands on one side thereof, to and over which is formed and bonded a polycrystalline diamond table.
U.S. Pat. No. 5,355,969 describes a cutting implement formed from a substrate of carbide, or other hard substance, bonded to a polycrystalline layer which serves as the cutting portion of the implement. The interface between the substrate and polycrystalline layer is defined by surface topography with radially spaced-apart protuberances and depressions forming smooth transitional surfaces.
U.S. Pat. No. 5,379,854 discloses a cutting element which has a metal carbide stud with a plurality of ridges formed in a reduced or full diameter hemispherical outer end portion of said metal carbide stud. The ridges extend outwardly beyond the outer end portion of the metal carbide stud. A layer of polycrystalline material, resistant to corrosive and abrasive materials, is disposed over the ridges and the outer end portion of the metal carbide stud to form a hemispherical cap.
U.S. Pat. No. 5,435,403 describes a cutting element having a substantially planar table of superhard material mounted on a substrate or backing.
U.S. Pat. No. 5,437,343 describes a diamond cutting element including a substantially planar diamond table having a periphery defined by a multiple chamfer.
U.S. Pat. No. 5,443,565 describes a drill bit characterized by a body fitted with multiple, spaced blades having a forward sweep relative to the center of the bit and cutting elements embedded in the blades at a selected back rake and side rake.
U.S. Pat. No. 5,460,233 describes a rotary drag bit for drilling hard rock formations with substantially planar PDC cutting elements having diamond tables backed by substrates which flare or taper laterally outwardly and rearwardly of the cutting edge of the diamond table.
U.S. Pat. No. 5,472,376 describes a tool component comprising an abrasive compact layer bonded to a cemented carbide substrate along an interface.
U.S. Pat. No. 5,486,137 discloses an abrasive tool insert having an abrasive particle layer having an upper surface, an outer periphery, and a lower surface integrally formed on a substrate which defines an interface therebetween.
U.S. Pat. No. 5,494,477 describes an abrasive tool insert comprising a cemented substrate and a polycrystalline diamond layer formed thereon by high pressure, high temperature processing.
U.S. Pat. No. 5,544,713 discloses a cutting element with a metal carbide stud that has a conic tip formed with a reduced diameter hemispherical outer tip end portion of said metal carbide stud. A corrosive and abrasive resistant polycrystalline material layer is also disposed over the outer end portion of the metal carbide stud to form a cap, and an alternate conic form has a flat tip face. A chisel insert has a transecting edge and opposing flat faces, which is also covered with a polycrystalline diamond compact layer.
U.K Pat. Application No. 2,240,797 A discloses a preform cutting element for a rotary drill bit comprising a polycrystalline diamond cutting table bonded to a coextensive substrate of cemented tungsten carbide.
Descriptions of methods for applying a layer or pocket of polycrystalline diamond to a sintered carbide substrate can be found in some of the afore-mentioned patents. Ordinarily, the method of sintering polycrystalline diamond to a top surface on a cylindrically shaped substrate is taught. This top surface may be flat, or shaped and is frequently non-planar. Some patents teach the application of diamond to a carbide substrate with a transition layer between the diamond and the substrate, said transition layer being a mixture of diamond and carbide. Still other patents reveal the use of diamond-filled pockets and grooves in a carbide substrate, with no continuous diamond surface covering the entire substrate upper surface or with a continuous coverage of a flat surface with irregularities. Related substrates are characterized by a hemispherical outer end portion with a plurality of ridges that extend outwardly. Some techniques use CVD or PVD films applied to the substrate prior to the high pressure and high temperature attachment of the diamond layer to the substrate. Embodiments are also produced by applying some of the afore-mentioned techniques to a heterogeneous substrate that in some instances has an eta-phase core.
Many related inventions have embodiments with irregularities in the substrate's top surface. Such irregularities ordinarily give rise to sharp features in the form of edges and corners. Due to stress concentration, these sharp features are known to be typical loci of crack formation. While surface topography improves attachment area and mechanical resistance to laminar shear, it must be observed that sharp surfaces cause stress to be concentrated not only under service loads, but also due to residual stress present within inserts under no applied external load.
The combination of diamond and carbide in a composite insert provides superior abrasion resistance and impact resistance while in service. Shear and percussion tools for drilling or cutting through rock or other hard materials also benefit from the insert's high abrasion and impact resistance. Amongst the different forms of diamond, polycrystalline diamond is particularly useful as an abrasion and corrosion resistant material. The most common geometric configuration for inserts is embodied by a cylindrical substrate with flat, conical, hemispherical, ovoidal, or other top surface, which is coated with polycrystalline diamond. The cylinder's top surface may also be modified to hold pockets or grooves of diamond, a practice common with flat diamond/substrate interfaces and familiar to those well versed in the art. Each of the afore-mentioned patents and elements of related art is hereby incorporated by reference in its entirety for the material disclosed therein.